BPMN 2 is the standard notation for describing business process models.
edoras bpm Modeler is compliant with BPMN2, this allows you to import and export models in BPMN v.2 format.
How does the BPMN 2 format work? How can we maintain application-specific additions to a workflow when using it across different tools?
Well, this is just a part of the standard. Standard-compliant BPMN v.2 tools will preserve other tools' settings even if the products don't implement them.